Digital signal cross-connection bays or equipments in use today are generally manually operated interconnection systems. Hardware comprises a relay rack with mounted panels equipped with jacks, and mounting bars or panels arranged with terminal strips. It is a common point within a central office at which digital signal equipments are cross-connected to establish telecommunication circuits and where the digital equipment is monitored and temporarily patched for maintenance purposes. Circuit testing, patching, and rearranging are functions performed at the digital signal cross-connection bays.
Cross-connections are typically run on the rear of the digital signal cross-connection bays. The physical configuration of terminals (wiring lugs) and jumper pathways used in existing digital signal cross-connection designs is not conducive to efficient and accurate wiring. Narrow aisles with insufficient lighting compound the operations difficulties. As the digital signal cross-connection frame increases in size (number of bays), the quantity of jumpers placed increases to a point where the capacity of the jumper pathways is often beyond design limits. The resulting jumper congestion adds to the inefficiency of the jumper running operation.
When maintenance or testing is required on a digital circuit the signals are accessed at the front of the digital cross-connection bay by means of jacks. These jacks are grouped in sets, one per system, and wired to permit the signal to be monitored or patched (using plugin cords) as needed. Every equipment termination at the digital cross-connection equipment is provided with a set of jacks. Human factors limit the amount of miniaturization possible so that jacks occupy a significant amount of space.
The digital signal cross-connection bays required in large installations often exceed that which can be placed in a single continuous aisle. When more than one lineup of digital signal cross-connection equipment is required, electrical access between the aisles is provided by tie cables. For a variety of reasons it is often necessary to locate the digital signal cross-connection equipment line-ups at a considerable distance from each other. When this occurs the tie pairs require gain devices and jacks on both of the digital cross-connection aisles to be served. This arrangement is costly, difficult to install, difficult to maintain, and contributes significantly to the digital signal cross-connection congestion.
There have also been proposals in the art fully to automate the cross-connection and testing functions. However, this can be very expensive considering the large cross-connection installations that are encountered in the field.